I'm not sure if this applies to all bonus rounds or not (didn't have time to test it), but on the final round if there's an early outbreak bonus then instead of one exit being blocked for engineer, both will be blocked. Hence the engineer will be stuck in spawn. https://steamcommunity.com/sharedfiles/filedetails/?id=1892215631 https://steamcommunity.com/sharedfiles/filedetails/?id=1892215588 https://steamcommunity.com/sharedfiles/filedetails/?id=1892215538 ^ these pictures were taken while I was playing with this other guy, I presume he was stuck in medic spawn too, although I'm not sure.
This is an entity firing problem, not a result of the bonus round. zs_steel has this issue from time to time on random rounds, especially when there are more players than normal, because server logic isn't perfect. i don't believe there is anything we can do to combat this.